WO2001060892A1

WO2001060892A1 - Use of hydrophilic (co)polymers in crosslinkable aqueous silicone emulsions

Info

Publication number: WO2001060892A1
Application number: PCT/FR2001/000435
Authority: WO
Inventors: Jean-Paul Benayoun; Christian Mirou; Charles Phan; Kenneth Wong
Original assignee: Rhodia Chimie
Priority date: 2000-02-15
Filing date: 2001-02-14
Publication date: 2001-08-23
Also published as: EP1263843A1; ATE385244T1; BR0108108A; EP1263843B1; FR2804963A1; BR0108108B8; CA2398705A1; FR2804963B1; US20030143408A1; ES2301531T3; DE60132657D1; NO20023832D0; US20050089697A1; DE60132657T2; NO20023832L; BR0108108B1; AU2001235677A1; US20070099007A1; NO336940B1; CA2398705C

Abstract

The invention concerns an aqueous silicone emulsion for use in particular in preparing a release coating on fibrous supports or for instance made of paper. Said emulsion comprises polyorganosiloxanes (POS) with Sy-vinyl units and POS with SiH units, crosslinkable by polyaddition in the presence of a platinum catalyst. The inventive emulsion consists in the use of at least a hydrophilic stabilising (co)polymer with molar mass Mw ≥ 105 g/mol, preferably Mw ≥ 5.105 g/mol for improving coalescence stability under shearing of aqueous silicone emulsions, capable of crosslinking to form release coatings on paper supports, and/or for improving regularity and homogeneity of the deposit of crosslinkable aqueous silicone emulsions, on both surfaces of a paper support, and/or for reducing the deposits of crosslinkable aqueous silicone emulsions to form release coatings on paper supports and/or for limiting, even eliminating, the tendency to foam which crosslinkable aqueous silicone emulsions exhibit to form release coatings on flexible supports.

Description

USE OF HYDROPHILIC ⁽ CO ⁾ POLYMERS IN AQUEOUS, CROSSLINKABLE SILICONE EMULSIONS.

TECHNICAL FIELD: The field of the invention is that of crosslinkable or crosslinked silicone compositions which can be used, in particular, to form a water-repellent and non-stick coating or film for fibrous or non-fibrous support, for example paper or the like. , or even in natural or synthetic polymer. More specifically, the invention relates to aqueous silicone dispersions or emulsions of the type comprising that:

^{• functionalized} polyorganosiloxanes (POS) carrying, on the same molecule or not:

• -a- of Si-H and Si-IE units with IE representing a group comprising at least one ethylenic unsaturation, preferably vinyl; the Si-H units being capable of reacting with the Si-IE units by polyaddition;

• -b- and / or Si-OR ° units (with R ° representing a C1-C6 alkyl) capable of reacting with one another by polycondensation;

20 • -c- and / or of Si-OR ° units (with R ° representing a C1-alkyl)

C6) and Si-H units capable of reacting with each other by dehydrogenocondensation;

• -d- of reactive units capable of reacting with one another by the cationic and / or radical route (eg acrylate or epoxy units);

A catalyst - C - suitable for the abovementioned reactions, respectively: -a- metallic preferably platinum, -b- and -c- metallic preferably stanous, -d- cationic and / or radical photoinitiator (eg salts of onium); - other additives (fillers, accelerators, inhibitors, pigments, surfactants).

The invention also relates to the preparation of this type of aqueous silicone emulsion.

Also contemplated herein are the methods of making crosslinked silicone articles, including coatings such as water repellents and / or release agents for fibrous or non-fibrous media (paper), from the above emulsion. PRIOR ART:

Polyorganosiloxanes are known for their ability to make surfaces of various supports non-stick (e.g. paper, fabric, polymer film or others). Non-stick treatments are easy to carry out with silicones, because the latter can be in the form of polymer, solution or liquid crosslinkable emulsion, which are easily applicable and spreadable on supports, at a rate and on an industrial scale. Thus, the silicone compositions are, for example, used as a release agent, in particular in the manufacture of tires and in the injection of plastics, or else for the coating of metal molds used in pastry making or in fillets. bread ovens or finally for the production of adhesive protective paper (label, decorative paper), interlayer paper for handling sticky masses (laminate, raw rubber), non-stick paper for baking pastries. By way of illustration, it can be indicated that US-A applications or patents

4,347,346, EP-A-0 219 720, EP-A-0 454 130 and EP-A-0 523 660 describe polyorganosiloxanes, intended to be used in the paper release application.

The silicone compositions according to the prior art referred to above are used in this field of paper anti-adhesion, in the form of emulsion baths (or coating baths) which serve to coat the film supports, which are then crosslinked under thermal activation and / or under radiation (UV, electron beam), to form the water-repellent and non-stick coating.

The aqueous silicone emulsion systems of particular interest in the context of this presentation are those containing polyorganosiloxanes (POS) with Si-H units and POSs with Si-vinyl units. Conventionally, these systems polymerize by platinum catalysis, according to a polyaddition mechanism (also called hydrosilylation) Si-H / Si-Vi.

Apart from POS Si-H and POS Si-Vi and the platinum catalyst, these emulsions may contain one or more water-soluble species such as hydroxyethylcellulose, starch, polyvinyl alcohol, etc. having in particular an emulsifying role. , thickener and stabilizer, but also the role of promoting two antinomic effects namely: anti-adhesion and printability. Surfactants can also be used in the composition of such emulsions. The aqueous silicone emulsion baths of the state of the art suffered, for a certain time, from a certain chemical instability resulting in the production of unwanted (chemical) gel and foam. These gels come from a premature addition reaction between Si-Vi units and Si-H units, which lead to the bridging of silicon atoms, hence a certain increase in the viscosity of the medium. The foams result from parasitic reaction of dehydrogeno-condensation between the Si-H groups of the POSs contained in the bath and the hydroxyl groups provided by the water and other additives of these emulsions.

The known aqueous emulsion baths also had another major drawback, namely a physical instability which is cumulative with the chemical instability mentioned above. Indeed, as soon as the emulsion is subjected to shearing (agitation), which is particularly the case when the emulsion circulates in industrial coating machines (in particular at the level of pumps or coating heads) , there is a phenomenon of coalescence of the droplets of dispersed silicone phase. This results in gelation, resulting in a loss of reactivity and a lower quality of the coating, in particular with regard to non-sticking. This phenomenon is aggravated by the fact that the temperature of the emulsion can increase as it circulates in industrial coating machines. This problem of coalescence under shear arises all the more acutely for coating systems with engraved cylinders. In fact, as soon as, due to the coalescence, a certain particle size is exceeded for the dispersed phase, the latter does not fill or badly fills the roughnesses engraved on the coating cylinder. Under these conditions, it is clear that the coating is of lower quality.

It is therefore important to combat this premature coalescence under shearing because it harms the coating, the crosslinking kinetics and therefore, ultimately, the quality of the non-stick coating deposited on the support, for example paper.

The applicant has succeeded in solving the problem of chemical instability (gel and foam) and partially the problem of physical instability (coalescence under shear) in the baths of aqueous silicone emulsions intended to crosslink to form non-stick coatings eg for paper, by proposing the use as an additive in these emulsions of an agent for fixing and maintaining the pH between 6 and 8, this agent advantageously being a buffer system such as NaHCO ₃ . This invention is described in International PCT Application WO PCT / FR98 / 02858 (WO 99/35181).

The aqueous silicone emulsions according to this PCT application remain perfectible, as regards their resistance to coalescence under shear. In addition, with regard to their properties to transform into crosslinked silicone coating non-stick on flexible support, for example paper, it has been found that a need remains with regard to the improvement of the homogeneity and the regularity of the deposition of the emulsion on the two faces of a flexible support, for example made of paper. The regularity of the silicone deposits on either side of the support is sought because it. facilitates the adjustment of the coating heads and makes it possible to adjust, at least and without risk, the deposition of the silicone layer.

In addition, it is also sought to reduce the silicone deposits on the cylinders of the coating machine. These residual silicone deposits pose maintenance problems and disturb the smooth running of the coating deposits, in particular, in the case where the coating machine comprises drying rolls.

Progress therefore remains to be made on the following aspects: *> coalescence under shear, *> regularity of the deposit on both sides of the support, * reduction of residual silicone deposits on the rolls of the coating machine, ^" > and maintenance , or even improvement, anti-foaming properties, which can go as far as suppressing untimely foaming.

Furthermore, through American patents Nos ^. 5,108,782 & 5,229,212, aqueous silicone emulsions precursors of non-stick coatings are known. These emulsions comprise a dispersed silicone phase based on polydimethylsiloxane bearing Si-H units, polydimethylsiloxane containing Si-Vinyl units and a catalyst based on a platinum complex, while the homogeneous aqueous phase of these emulsions comprises a thickening agent polymer dispersible in water or soluble in water, namely a polyoxyethylene (trade name: "POLYOX WSR-301" / Union Carbide). The dry matter of these emulsions comprises 94% by weight of silicone 4.5% by weight of catalyzing emulsion and 1.5% by weight of polyoxyethylene.

Like all thickeners conventionally used in aqueous silicone emulsions of this type, polyoxyethylene is a thickener which is intended to increase the resistance of the silicone on the surface of the support, by preventing it to get inside of it. The thickeners according to these US patents act by increasing the viscosity of the emulsion and by their capacity to trap water.

The hydrophilic polymeric thickening agent, preferably retained in these previous American patents, is included in a range of molecular weights going from 1.10 ⁵ g / mole to 10.10 ⁶ g / mole. In addition, when it is polyethylene oxide, the preferred molar mass is then between 5.10 ⁵ and

1.10 ⁶ g / mole.

In addition to polyoxyethylene, the thickening agent according to these American patents can be chosen from polyoxypropylenes, propylene oxide / ethylene copolymers or polyacrylamides.

In addition, it should be noted that these previous American patents do not allude to the improvement: o of the stability to coalescence under shearing, o of the regularity and the homogeneity of the deposits of silicone emulsions on the two faces a flexible support, for example made of paper, no more than a reduction in the silicone deposits on the cylinders of the coating machine after application of an aqueous silicone emulsion film, and even less a reduction in the unwanted foaming.

BRIEF STATEMENT OF THE INVENTION:

In such a state of the art, the applicant has set itself the essential objective of updating a new additive for aqueous silicone emulsion:

* with a view to improving their stability to coalescence under shear, * and / or with a view to perfecting the regularity and homogeneity of the deposition of a silicone emulsion film on the two faces of a flexible support, for example in paper,

* and / or with a view to limiting the residual deposits of silicone on the rolls of the coating machine, after deposition of the silicone emulsion film, * and / or with a view to reducing or even eliminating the formation of foams.

Another essential objective of the invention is to propose a process for the preparation of the aqueous silicone emulsions mentioned above.

Another objective of the invention is to provide flexible supports, for example made of paper, having a good quality non-stick crosslinked silicone coating in terms of coating and non-sticking; this coating: • moreover forming a regular deposit on either side of the flexible support, for example made of paper,

• not causing silicone to deposit on the rollers of the coating machine, “and offering good gloss and retention properties on the surface of the support.

These objectives among others are achieved by the present invention which firstly proposes the use of at least one hydrophilic stabilizing (co) polymer of molar mass Mw> 1.10 ⁵ g / mole, preferably Mw> 5.10 ⁵ g / mole:> to improve the stability to coalescence under shearing of aqueous silicone emulsions capable of crosslinking to form non-stick coatings on flexible supports, for example made of paper,

> and / or to improve the regularity and homogeneity of the deposition of crosslinkable aqueous silicone emulsions, on the two faces of flexible supports, for example made of paper,

> and / or to reduce the deposits of aqueous silicone emulsions capable of crosslinking to form non-stick coatings on flexible supports, for example made of paper, and / or to limit or even eliminate the tendency to foam that silicone emulsions have aqueous materials capable of crosslinking to form non-stick coatings on flexible supports, for example paper. (Mw: average molar mass).

Thus, thanks to the use of this additive, aqueous silicone emulsions in particular for forming non-stick coatings on flexible supports (paper) are no longer subject to the phenomenon of coalescence under shear. They retain their properties at the application level, namely: they adhere perfectly to the support, for example paper, they are easily and correctly in the form of film and their crosslinking takes place quickly and sufficiently. Thus, these emulsions in which a judiciously selected hydrophilic stabilizer is used, in accordance with the invention, are capable of forming quality non-stick layers.

The improvement in shear stability (non-coalescence) provided by the additive used according to the invention to aqueous silicone emulsions is based on the contribution of a particular rheological property to the continuous phase. The property in question is the elongational viscosity η _e ,. So, in accordance with the inversion, macromolecules are selected which promote elongational viscosity η _e ι The hydrophilic polymers retained tend to transform the regime of turbulence which the emulsion undergoes when it is under agitation (under shear), into a laminar regime. This makes it possible to limit the shocks between the particles of dispersed phase, and therefore to slow down the proscribed coalescence.

DETAILED DESCRIPTION OF THE INVENTION:

According to a preferred characteristic of the invention, the stabilizer is chosen from the group of hydrophilic (co) polymers comprising:

-a- aliphatic polyethers obtained from monomers comprising at least one linear or branched alkylene residue having from 1 to 6 carbon atoms, preferably: o poly (methylene oxide) o poly (ethylene oxide) o poly (propylene oxide) o copoly (methylene oxide) (propylene oxide) o polyoxethane o copoly (methylene oxide) (propylene oxide); -b- (co) polyacrylamides obtained by copolymerization of acrylamide with one or more copolymerizable comonomer (s); -c- polysaccharides:

* natural of animal origin such as in particular chitosan and chitin, * natural of vegetable origin: such as in particular carrageenans, alginates, gum arabic, guar, caroub, tara, cassia, konjak, mannan; guars, alginates, carob gums being more particularly appreciated, and / or starch and its derivatives and / or cellulose and its derivatives, carboxymethylcellulose, methylcellulose, ethylcellulose, hydroxymethylcellulose, cyanoethylated starch , the carboxymethyl starch being particularly selected; * and / or those of bacterial origin (biogums), in particular those obtained by fermentation of a carbohydrate under the action of a microorganism, xanthan gums obtained by fermentation under microorganisms belonging to the genus Xanthomonas,

-d- polyacrylates:

coord

Rd representing a linear or branched C1-Cl 2 alkyl or a C5-C6 cycloalkyl.

These judiciously added polymer additives make it possible to increase the elongational viscosity, which limits or eliminates turbulence and reduces the resistance encountered by the particles of dispersed silicone phase in the emulsion.

The additives a, b, c and d promoters of elongational viscosity are long and flexible hydrophilic macromolecules of high molecular weight Mw. In practice, these are polymers of high molecular mass Mw or even giant micelles.

As regards the molecular mass Mw, that of the stabilizers a or b used in the use according to the invention is defined as follows (in g / mole): more preferably still Mw> 1.10 ⁶ more especially still Mw> 3.10 ⁶ and in practice ... 20.10 ⁶ >Mw> 4.10 ⁶ .

Furthermore, these stabilizers of the a - (co) polyalkylene oxide - or b - (co) polyacrylamide- type, are used at a concentration Cs, expressed in% by weight relative to the mass of POS of the emulsion, such than :

0.1 <Cs <5 preferably 0.5 <Cs <2.

As soon as the stabilizer is a type c polysaccharide, it is preferable that it is a polymer whose Mw (in g / mole) is such that:

more preferably still Mw> 1.10 ° more especially still Mw ≥ 3.10 ^b and in practice 20.10 ⁶ >Mw> 5.10 ⁵ .

In such a scenario, the concentration Cs of stabilizer - c - in the emulsion is defined as follows (expressed in% by weight relative to the mass of POS of the emulsion):

0.05 <Cs <5 preferably 0.1 <Cs <2.

As an example of a - a - type stabilizer, there may be mentioned

The poly (ethylene oxide) of formula ai:

Polypropylene oxides of formula a2

In the above formulas ai and a2, n, n 'are chosen so as to obtain the molar masses defined above.

By way of example of polyacrylamide, mention may be made of those of formula b

m is chosen so as to obtain the molar masses defined above. It is to the credit of the applicant to have determined a reliable and reproducible selection criterion for the selection of the promoter stabilizer of elongational viscosity. Thus, this stabilizer is chosen so that the emulsion has the following particle size characteristics, with regard to the dispersed silicone phase:

D ₅₀ <7 μm, preferably <3 μm D ₉₀ ≤ 20 μm preferably <10 μm after 4 hours in a stability test T and for an initial particle size such as:

D ₅₀ ≤ 0.7 μm D ₉₀ <1.5 μm

D ₅₀ = diameter below which at least 50% of the particle population is located.

D ₉₀ = diameter below which at least 90% of the particle population is located.

More precisely, within the meaning of the invention, the parameter D ₅₀ (or D ₉₀ ) is the median size of the particle size distribution. It can be determined on the cumulative particle size distribution graph, obtained by one of the analytical techniques mentioned below, by determining the size corresponding to the cumulation of 50% (or 90%) of the population of particles. Concretely, this particle size parameter D ₅₀ (or D ₉₀ ) corresponds to the maximum average dimension of at least 50% (or 90%) of the mass of particles considered, a D ₅₀ (or D ₉₀ ) of 10 μm indicates that 50 % (or 90%) of the particles have a size less than 10 μm. Granulometry measurements can be carried out by conventional techniques such as sedimentation, laser diffraction (for example COULTER® LSI30), optical microscopy coupled with image analysis, etc.

The stability test T is defined below. A glass beaker 7.5 cm in diameter and 13 cm in length thermostatically controlled at 30 ° C. is used. The blade used is a propeller blade (3 blades) 3 cm in diameter and is located at a distance of 2 cm from the bottom of the beaker. The stirring speed is 2000 rpm.

Every hour, a sample is taken and the size of the emulsion is measured on a HORIBA granulometer. This stability test T highlights the absence of coalescence under shear of the aqueous silicone emulsion additivated by the selected stabilizer (s).

The use in accordance with the invention of said stabilizer can also have the effect of improving the regularity and the homogeneity of the emulsion deposit in a layer on both sides of a paper support. Thanks to the stabilizer, the emulsion coating in layers is almost identical on both sides of the paper. The regularity and homogeneity of the silicone deposits are measured in grams per m ² according to the X-ray fluorescence method on an apparatus of the Oxford X-Ray 3000 type, on both sides of the paper. These deposits are produced by coating on a "size press" type machine, with a non-porous parchment paper support. Crosslinking takes place at 130 ° C.

Another effect sought through the use of a hydrophilic polymeric stabilizer is the reduction of silicone deposits on the rollers of the coating machine ("reduction of Dusts"). This reduction is assessed visually. The same applies with regard to the limitation or even the annihilation of the formation of undesirable foams. In this regard, it should be noted that this advantageous function of the stabilizer used in accordance with the invention makes it possible to avoid or limit the use of an anti-foam. Insofar as the stabilizer used in accordance with the invention also limits the penetration of the silicone into the flexible support, for example paper, it may be envisaged to reduce the dry extract of the aqueous silicone emulsions used in coating to form anti- paper adhesion. This results in a significant saving, which constitutes an important asset of the invention. The emulsions concerned by the use in accordance with the invention are of the type comprising those:

- A - at least one polyorganosiloxane (POS) carrying Si-alkenyl crosslinking units, preferably Si-Vi;

- B - at least one POS carrying Si-H crosslinking patterns; - AB - and / or at least one POS carrying Si-alkenyl and Si-H units;

- C - at least one polyaddition catalyst, preferably based on platinum;

- D - at least one stabilizer as defined above;

- E - at least one crosslinking inhibitor, preferably chosen from acetylenic alcohols; - F - and / or at least one agent for fixing and maintaining the pH (preferably a buffer and more preferably still NaHCO ₃ );

- G - optionally at least one surfactant;

- H - optionally at least one polyvinyl alcohol APV as defined below;

- I - optionally at least one other additive chosen from bactericides, and / or anti-freeze agents, and / or wetting agents, and / or anti-foam agents and / or fillers, and / or synthetic latexes, and / or dyes, and / or acidifiers.

Preferably, at least one POS A of the alkenyl Si type, for example Si-Vi, and at least one POS B of the Si-H type are used.

POS A is by weight one of the essential constituents of the emulsion.

Advantageously, this POS A is a product comprising units of formula:

^WaZ _b ^Si0 4- (a + b) ^{<A "1>}

2

in which: - W is an alkenyl group, preferably vinyl or allyl,

- Z is a monovalent hydrocarbon group, free from any adverse action on the activity of the catalyst and preferably chosen from alkyl groups having from 1 to 8 carbon atoms included, advantageously, from methyl, ethyl, propyl and 3,3,3-trifluoropropyl and also among the aryl groups and, advantageously, among the xylyl and totyl and phenyl radicals,

- a is 1 or 2, b is 0, 1 or 2 and a + b is between 1 and 3, possibly at least some of the other units are units of average formula:

^zcSi0 4- (c) ^{<A 2>}

2 in which Z has the same meaning as above and ca a value between 0 and 3, for example between 1 and 3. Z is generally chosen from methyl, ethyl and phenyl radicals, at least 60 mol% of the radicals Z being methyl radicals.

It is advantageous that this polydiorganosiloxane has a viscosity (at 25 ° C) at least equal to 10 mPa.s, preferably between 50 and 1,000 mPa.s.

All the viscosities in question in this presentation correspond to a quantity of dynamic viscosity at 25 ° C called "Newtonian", that is to say the dynamic viscosity which is measured, in a manner known per se, at a gradient sufficiently low shear speed so that the viscosity measured is independent of the speed gradient.

The polyorganosiloxane A can be formed only of units of formula (A.1) or can additionally contain units of formula (A.2). Likewise, it can have a linear, branched, cyclic or network structure. Its degree of polymerization is preferably between 2 and 5000. Examples of siloxyl units of formula (A.1) are the vinyldimethylsiloxane unit, the vinylphenylmethylsiloxane unit and the vinylsiloxane unit.

Examples of siloxyl units of formula (A.2) are the SiO ₂ , dimethylsiloxane, methylphenylsiloxane, diphenylsiloxane, methylsiloxane and phenylsiloxane units. Examples of polyorganosiloxanes A are dimethylpolysiloxanes with dimethylvinylsilyl ends, methylvinyldimethylpolysiloxane copolymers with trimethylsilyl ends, methylvinyldimethylpolysiioxane copolymers with dimethylvinylsilyl ends, cyclic methylvinylpolysiloxanes.

Polyorganosiloxane B is preferably of the type of those comprising siloxyl units of formula:

H _d L _e SiO _{4, (d + e)} (B.1)

2

in which :

L is a monovalent hydrocarbon group, free from any adverse action on the activity of the catalyst and preferably chosen from alkyl groups having from 1 to 8 carbon atoms included and, advantageously, from methyl, ethyl, propyl and 3,3,3-trifluoropropyl and also among the aryl groups and, advantageously, among the xylyl and totyl and phenyl radicals, d is 1 or 2, e is 0, 1 or 2, d + has a value between 1 and 3 optionally, at least part of the other motifs being motifs of medium formula:

^L - ^If O 4-g < ^B - ² )

2

in which L has the same meaning as above and g has a value between 0 and 3. The dynamic viscosity η _d (at 25 ° C) of this polyorganosiloxane B> to 5 preferably to 10 and, more preferably still, is between 20 and 1000 mPa. s.

Polyorganosiloxane B can be formed solely of units of formula (11.1) or additionally comprises units of formula (B.2). Polyorganosiloxane B can have a linear, branched, cyclic or network structure. The degree of polymerization is greater than or equal to 2. More generally, it is less than 5,000.

Examples of units of formula (B.1) are: H (CH ₃ ) ₂ SiO _1/2 , HCHaSiO ^, H (C ₆ H ₅ ) SiO _2/2 The examples of units of formula (B.2) are the same as those given above for the reasons of formula (A.2).

Examples of polyorganosiloxane B are:

- dimethylpolysiloxanes with hydrogenodimethylsilyl ends, poly (dimethylsiloxane) (methylhydrogenosiloxy) α, ω-dimethylhydrogenosiloxane.

- copolymers with dimethyl-hydrogenomethylpolysiloxane (dimethyl) units with trimethylsilyl ends, copolymers with dimethyl-hydrogenomethylpolysiloxane units with hydrogenodimethylsilyl ends, - hydrogenomethylpolysiloxanes with trimethylsilyl ends,

- cyclic hydrogenomethylpolysiloxanes.

The bases of polyaddition silicone compositions may contain only linear polyorganosiloxanes A and B such as, for example, those described in the patents: US-A-3,220,972, US-A-3,697,473 and US-A-4,340,709 or comprise both branched or networked polyorganosiloxanes A and B, such as for example those described in the patents: US-A-3,284,406 and US-A-3,434,366.

Catalysts C are also well known. The platinum and rhodium compounds are preferably used. It is possible, in particular, to use the complexes of platinum and of an organic product described in the patents US-A- 3 159 601, US-A-3 15 £ ^> 602, US-A-3 220 972 and the European patents EP-A- 0 057 459, EP-A-0 188 678 and EP-A-0 190 530, the platinum and vinyl organosiloxane complexes described in US-A-3,419,593, US-A-3,715,334, US-A-3,377,432 and US-A-3,814,730. The generally preferred catalyst is platinum. In this case, the weight quantity of catalyst C, calculated by weight of platinum metal, is generally between 2 and 400 ppm, preferably between 5 and 200 ppm based on the total weight of polyorganosiloxanes A and B.

The agent F for fixing and maintaining the pH is preferably a buffer system comprising HCθ3 ^" Cθ3 ^2_ and / or H ₂ PO ₄ 7HPO ² - _4. Thus, to obtain the desired buffering effect, it will be necessary to introduce in accordance with the invention a salt of HC03 ^" and or H ₂ PO ₄ " such as NaHCO _β and / or Na ₂ CO ₃ and / or NaH ₂ PO ₄ and / or Na ₂ HPO _4. It goes without saying that any other salt with a different counter anion (eg K) could be suitable. In a particularly preferred manner, a buffer system consisting of NaHCO ₃ which is incorporated into the emulsion is used in practice.

According to a variant, the buffer system can be a means allowing regulation of the pH of the emulsion by monitoring the evolution of its pH and correcting its variations by incorporating into the emulsion suitable quantities of at least one agent -F-, which can be an acid or a base depending on the direction of variation of the pH.

The acid or base added to the emulsion as necessary, as agent -F-, for the exogenous regulation of the pH, perhaps mineral or organic. It can also be a strong (or weak) acid or strong (or weak) base salt. As examples of strong bases, there may be mentioned: triethanolamine, soda or potash.

Advantageously, the catalytic system of this polyaddition type silicone elastomer emulsion comprises at least one stabilizer E or retarder of the addition reaction (crosslinking inhibitor), chosen from the following compounds: - polyorganosiloxanes, advantageously cyclic and substituted with at least an alkenyl, tetramethylvinyltetrasiloxane being particularly preferred, pyridine, phosphines and organic phosphites, - unsaturated amides, alkylated maleates, and acetylenic alcohols. These acetylenic alcohols, (Cf. FR-B-1 528 464 and FR-A-2 372 874), which are part of the preferred hydrosilylation reaction thermal blockers, have the formula: R ¹ - (R ² ) C ( OH) - C ≡ CH formula in which,

. R ¹ is a linear or branched alkyl radical, or a phenyl radical; . R ² is H or a linear or branched alkyl radical, or a phenyl radical; the radicals R ¹ , R ² and the carbon atom located at a of the triple bond which can optionally form a ring; the total number of carbon atoms contained in R ¹ and R ² being at least 5, preferably from 9 to 20.

Said alcohols E are preferably chosen from those having a boiling point above 250 ° C. As examples, we can cite:. ethynyl-1-cyclohexanol-1;

. methyl-3-dodecyne-1-ol-3; . trimethyl-3,7,11-dodécyne-1-ol-3; . diphenyl-1, 1-propyne-2-ol-1; . 3-ethyl-6-nonyne-1-ol-3-ethyl; . methyl-3-pentadecyne-1-ol-3.

These α-acetylenic alcohols are commercial products. Such a retarder E is present at a rate of 3000 ppm at most, preferably at the rate of 100 to 2000 ppm relative to the total weight of the organopolysiloxanes (A) and (B). The surfactant (s) (G) which may be present in the emulsion according to the invention as an emulsifying agent are of non-ionic or ionic nature.

In practice, it is possible to use as nonionic alkyl phenols, fatty alcohols or fatty acids carrying alkylene oxide groups, for example ethyiene or propylene eg: nonylphenol comprising between 9 and 30 ethylene oxide (EO) or acid groups oleic with 2 to 8 EO.

The ionic surfactants, preferably anionic, which can be used are, eg sulfates, sulfonates, phosphates, sulfosuccinates, sulfosuccinamates, sulfoacetates, or derivatives of amino acids. For more details on the available surfactants, reference is made to the reference works, and for example to the article published in "Chemistry Information No. 146 - June- July 1975 - p. 1 19-126".

With regard to the water-soluble emulsifying agents -G- of the protective colloid type, it should be observed that, in addition to their emulsifying function, these emulsifying agents -G- can also be active as promoters of the anti -adhesion, water repellency, or even printability, with regard to the field of paper anti-adhesion. This is precisely the case of Polyvinyl Alcohols (PVA) which can be used as an optional additive -H- in the context of the invention. Thus, PVA can play the role of emulsifiers -G- and additives -H-.

Polyvinyl alcohols (PVA) -H- are compounds obtained indirectly from their esters, by hydrolysis in an aqueous medium or by alcohol in an anhydrous medium. In practice, the esters used as raw material are commonly polyvinyl acetates. Generally, the lysis of the esters leading to the APV -H- is not complete. There remain in the molecule acyl radicals, the proportion of which influences the properties of the PVA -H-, in particular its solubility. A mode of definition of APV -H- is therefore based on the indication of the ester index (LE) which is inversely proportional to the rate of hydrolysis. Measuring the I.E. is carried out in a manner known per se, by neutralization of the possible acidity of the polyvinyl alcohol, saponification of the acyl groups and titration of the excess alkaline saponification.

Polyvinyl alcohols -H- are also characterized by their degree of condensation which can be evaluated by determining the dynamic viscosity of a standard solution (designated by η _dt in the present description), knowing that this variable is of the higher the greater the degree of condensation. The viscosity η _dt corresponds to the dynamic viscosity coefficient of an aqueous PVA solution at 4% by weight, measured at a temperature of 20 ± 5 ° C using a Brookfield viscometer. The APVs useful as an emulsifier -G- and or as an additive -H- have a molar mass Mw <10 ⁵ g / mol. It is therefore a PVA whose viscosity η _dt is between 3 and 40 mPa.s, preferably between 5 and 30 mPa.s, and whose degree of hydrolysis is between 60 and 100% in molecule, preferably between 75 and 90% by molecule. Polyvinyl acetates are conventional PVAs, which can be used in the invention. Furthermore, the emulsion according to the invention optionally contains one or more additives I, which can be inter alia:

- l-j = bactericidal agent such as for example sorbic acid,

- 12 = antifreeze and / or wetting agent such as for example glycols such as propylene or ethylene glycol,

- I3 = antifoam advantageously selected from silicone antifoams such as, for example, those sold by the applicant under the name RHODORSIL® 70414 marketed by RHODIA SILICONES, - I4 = preferably mineral filler chosen from siliceous materials or not, the siliceous fillers being more particularly preferred,

- I5 = synthetic latex coadditives associated with protective colloids H playing the role of emulsifiers and non-adhesion promoters (VPA); These synthetic latexes can be, for example, butadiene (co) polymers, acrylics, vinyl acetates, etc;

- \ Q = dye or pigment,

- 17 = acidifier such as for example acetic acid. Concerning the siliceous fillers I4, it should be noted that they can play the role of reinforcing or semi-reinforcing filler.

The reinforcing siliceous fillers are chosen from colloidal silicas, combustion and precipitation silica powders or a mixture thereof.

These powders have an average particle size generally less than 0.1 mm and a BET specific surface greater than 50 m ² / g, preferably between 150 and 350 m ² / g.

Semi-reinforcing siliceous fillers such as diatomaceous earth or ground quartz can also be used.

With regard to non-siliceous mineral materials, they can act as a semi-reinforcing or tamping mineral filler. Examples of these non-siliceous fillers which can be used alone or as a mixture are carbon black, titanium dioxide, aluminum oxide, hydrated alumina, expanded vermiculite, unexpanded vermiculite, calcium carbonate, l zinc oxide, mica, talc, iron oxide, barium sulfate and slaked lime. These fillers have a particle size generally between 0.001 and 300 mm and a BET surface area less than 100 m ² / g. In terms of weight, gold prefers to use an amount of filler between 20 and 50, preferably between 25 and 35% by weight relative to all the constituents of the composition.

According to an advantageous arrangement of the invention, the proportion of water in the emulsion is greater than or equal to 50% by weight, preferably greater than or equal to 55% by weight and for example in practice of the order of 55 - 60% by weight or even 85 to 90% by weight.

According to another of its aspects, the present invention relates to a process for the preparation of an aqueous silicone emulsion, usable in particular as a coating base for the production of non-stick and water-repellent coatings, this emulsion being of the type defined above. above. According to a preferred characteristic of the invention, the hydrophilic polymeric stabilizer is incorporated into the formulation before, during or after the formation of the aqueous silicone emulsion. The preparation of an emulsion according to the invention can be a mixture of two pre-emulsions, namely a basic pre-emulsion E- | and a catalyzing pre-emulsion E2, so as to produce an emulsion E3, which is diluted or not with water, so as to adjust the dry silicone extract according to the intended application (desired silicone deposition, type treated support and coating technique). As soon as there is an E3 emulsion prepared or not by the process described above and which has the advantage of not being subject to coalescence under shear, neither to expansion, nor to gelling, it It is particularly advantageous to be able to use it in applications for the manufacture of crosslinked silicone polymers and in particular non-stick silicone coatings.

It follows that according to another of its objects, the present invention relates to a process for producing a coating, in particular non-stick and water-repellent, on a fibrous or non-fibrous support, preferably made of paper, characterized in that it consists of: • coating the support with the emulsion described above, and / or as obtained by the process described above, • and ensuring that the coated layer crosslinks by providing, preferably, thermal activation . The coating is carried out by known and appropriate means, for example with a doctor blade, a "size-press" roller, an engraved cylinder or a "roll cake". The means for thermal activation of the crosslinking are conventionally ovens (for example tunnel ovens), hot rollers, or even infrared sources. This thermal activation can be supplemented by actinic activation and / or by electron bombardment. The coated supports are preferably fibrous supports and more preferably still paper or similar supports. In this application, the coating rate is less than or equal to 1.2 g silicone / m ² of support, preferably less than or equal to 0.9 g / m ² and more preferably still less than or equal to 0.50 g / m ² . As other examples of supports, mention may be made of those consisting of synthetic polymers such as polyethylenes, polypropylenes or polyesters or else of natural polymer.

It goes without saying that the supports can be in any form other than that of sheet or film. According to a preferred application of the emulsion according to the invention, the fibrous support or not comprises on at least one of its faces a non-stick and water-repellent coating (possibly printable) obtained by crosslinking of said emulsion. More specifically, this support may include the non-stick and water-repellent coating on one of these faces and an adhesive coating on the opposite face. In this embodiment, it is envisaged in particular articles such as labels, sheets, tapes or the like, self-adhesive which have the property of being water-repellent and printable, adhesive on each other in a reversible manner. This last characteristic is particularly interesting for self-adhesive labels because it allows the removal of conventional non-stick supports.

It goes without saying that the invention is not limited to supports with opposite adhesive / non-stick surfaces, it also encompasses all supports coated only with a layer of printable adhesive which can be printed and used as such, by example, as a means of protection. The following examples of preparation of the silicone emulsion under consideration and of its application as a non-stick and water-repellent coating for paper supports, will allow a better understanding and understanding of the invention. They will also bring out the variants and the advantages of said invention, the performance of which in terms of coalescence stability under shear in terms of regularity of silicone deposition on the faces and in terms of reduction of dusts will be highlighted by comparative tests. . DESCRIPTION OF THE FIGURES:

Figure 1 (Example 2) shows curves giving the evolution of the particle size parameter D ₅₀ (in μm) as a function of the shear time t (in hours) (Stability test T) for two aqueous POE 1 silicone oil emulsions and

POE 3 added with polyoxyethylene (POE) and for a control silicone emulsion E 1.2 without POE;

Figure 2 (example 2) shows curves giving the evolution of the particle size parameter D ₅₀ (in μm) as a function of the shear time t (in hours) (Stability test T) for two emulsions of POE 2 silicone oil and POE 3 comprising POE 2 and 3 (0.08%) and polyvinyl alcohol (PVA: 1%) and for a control silicone emulsion E 1.2 without POE;

Figure 3 (example 2) shows a curve (-O-) giving the evolution of the mean diameter (Dm) in μm and a curve (-D-) giving the evolution of the median diameter (Dm) in μm as a function of shear time t (in hours) (Stability test T) for an aqueous emulsion of silicone oil comprising 0.5% by weight of POE 3; Figure 4 (example 3) shows graphs giving the evolution of the mean diameter (Dm) in μm of the dispersed phase particles as a function of time t (in hours) for:

- [-x-x-]: an aqueous emulsion of silicone oil containing 1% of PVA (control);

- [-0-0-]: an aqueous emulsion of silicone oil containing 1% of PVA and polyacryamide (PAM) FA 920 up to 0.5% by weight; - [-Δ-Δ-]: an aqueous emulsion of silicone oil containing 1% PVA and polyacryamide (PAM) FA 920 up to 0.1% by weight; [-O-O-]: an aqueous emulsion of silicone oil containing 1% of PVA and polyacryamide (PAM) FA 920 up to 0.01% by weight; Figure 5 (example 3) shows a curve (-O-) giving the evolution of the mean diameter (Dm) in μm and a curve (-D-) giving the evolution of the median diameter (Dm) in μm as a function of shear time t (in hours) (Stability test T) for an aqueous emulsion of silicone oil comprising 0.1% by weight of PAM FA 920 VHM;

Figure 6 (example 4) shows a curve (-O-) giving the evolution of the mean diameter (Dm) in μm and a curve (-D-) giving the evolution of the median diameter (Dm) in μm as a function of shear time t (in hours) (Test of stability T) for an aqueous emulsion of silicone oil comprising 0.1% by weight of hydroxypropylguar.

. EXAMPLES

EXAMPLE 1

1.1 MATERIALS

1. Emulsion E3, 300 g, or silicone "option 25": The amount of emulsion used is 300 g, either:

- 82.2 g of option 25, ie an El.l emulsion at -1% APV 25/88 (polyvinyl alcohol) for -38% copoly (dimethyl) (methylvinyl) siloxane silicone oil with dimethylvinylsilyl ends (l ' Si-Vinyl oil) whose η _dt = 250 mPa.s and having about 0.75-1% by weight of vinyl;

- 2.9 g of emulsion E1.2 at 2% APV 25/88 and 38% of poly (methylhydrogen) siloxane silicone oil with trimethylsilyl ends (SiH oil) whose η _dt = 30 mPa. s and having approximately 30% by weight of Si-H functions; - 6 g of emulsion E2 with 2% of APV 25/88, 38% of polydimethylsiloxane silicone oil whose η _dt = 600 mPa.s and having about 0.4% by weight of vinyl (279), this emulsion containing a few ppm of platinum catalyst. The balance is deionized water.

2. polymers in solution (stabilizer D):

Q polyoxyethylene "POE" marketed by UNION CARBIDE: POE 1 POLYOX ® "WSRN-12K", Mw = 1.10 ⁶ g / mole * POE 2 POLYOX ® "WSR coagulant", Mw = 5.10 ⁶ g / mole POE 3 POLYOX ® "WSR -308 ", Mw = 8.10 ⁶ g / mole

Q polyacrylamide (PAM) of NMERICNN reference CYNNNMIDE FN920 (Mw = 8- 10 ⁶ g / mol _ιntπns η eq _ue = 1.3336) and reference FN920VHM (Mw> 9 10 ^6). α guars of RHODIN. 1.2 METHODS

Vortex measurement: A solution of 800 ml of water is stirred using a pale frame 15mm wide and 30mm long in a 1 liter test tube. The rotation speed, approximately -900 rpm, is adjusted to allow the vortex in the water to reach 75mm in height above the level of the water at rest. The polymer providing the elongational viscosity is added drop by drop. The height of the vortex is measured after 20 seconds.

Stability test T to evaluate the effect of hydrophilic polymer stabilizers (POE, PNM and guars) on the coalescence under shear of a base emulsion. This stability test is carried out in a glass beaker 7.5 cm in diameter and 13 cm in length thermostatically controlled at 30 ° C. The blade used is a propeller blade (3 blades) 3 cm in diameter and is located at a distance of 2 cm from the bottom of the beaker. The stirring speed is 2000 rpm. Every hour, a sample is taken and the size of the emulsion is measured on a HORIBN granulometer.

Attachment test: the attachment of the silicone coating is evaluated using a trade test consisting in rubbing the silicone surface with the index finger (10 back and forth) and observing the appearance of dust on the surface . No dust after 10 passes = excellent. Dust after 8 passes = good. Dust before 8 passages = bad.

Reactivity test: The reactivity of a bath coating is evaluated by the level of crosslinking after 30 seconds at 110 ° C. in an oven. We use the trade test called Loop Test to characterize the level of crosslinking: adhesive tack on tape adhesive after contact with the Siliconized surface.

Gloss: the gloss of the silicone layer is evaluated by a simple qualitative visual observation.

Wetting: this is the ability of the bath to wet the support during manual coating carried out in the Meyer bar laboratory. It is observed visually whether there is dewetting of the coating before placing in the oven for crosslinking. EXAMPLE 2 POLYOXYETHYLENE

We implement POE 1 and 3

2.1 The stability under shear brought to El.l by the POE.l and 3 (0.08%) is compared, compared to a reference emulsion El.2 without POE.

Figure 1 represents a curve of the evolution of D ₅₀ as a function of the shear time for POE1 & POE3 & ref. E1.2.

The POE2 of greater mass is the most effective in stabilizing the emulsion.

2.2 The stability under shear of an El.l emulsion is compared using POE 1 and 2 grading 800 ppm.

Figure 2 shows the evolution of D ₅ 0 as a function of shear time for emulsions with 1% PVA containing 0.08% of POE 2 and 3 and a reference emulsion El.2 without POE.

The application properties (see Table 1) are very good except for a slight decrease in gloss after 4 hours of shearing.

Table 1: Application properties of emulsions stabilized with poly oxyethylenes

0.08% POE 2 0.08% POE 3

Hrs hooked Reactivity Bπllanc cobb wet Wet hooked reactivity bπllanc cobb Wet

0 V V V v V H

1 V V V V H

2 V V V V v V V V H

3 V V V v V V V V

4 V Medium V V Medium V V Legend: V = GOOD V = VERY GOOD

POE OF LITTLE MASS

POEs of "small" mass do not develop elongational viscosity, but have a normal viscosity similar to POE of high mass. A POE 3 of Mw = 300K is used at a concentration of 0.5% by weight in an El.l. emulsion.

Figure 3 shows that the emulsion with 0.5% POE 3 additive has increased stability.

However, the application properties are poor, see the

Table 2 below.

Table 2: Application properties of emulsions stabilized with low-mass polyethylene oxides

0.08% POE 3 (300K) 0.5% POE 3 (300K)

Hrs hooked reactivity bπllanc Cobb wet Hrs hooked reactivity bπllanc cobb Wet o V V o Medium

1 X X X 1.5 medium X medium

4 X X X medium 4 V X medium

It can be concluded on the basis of the above results that the shear stability of the non-stick paper emulsion is obtained by the use of high-mass polymers developing an elongational viscosity.

EXAMPLE 3

Poly Acrylamide

The high molecular weight polyacrylamides (PAM) can also be used in accordance with the invention.

PAMs are used at different concentrations in an E 1.1 emulsion. The reference used is the Floerger FA920 from SNF.

These emulsions with or without PAM are subjected to the T stability test.

Figure 4 shows the evolution of coalescence under shear of an emulsion based on -1% in PVA (φ = 40%, Dso ~ 1.5 μm) containing polyacrylamide Floerger FA920.de 100 to 5000 ppm. Figure 4 shows that the PNM FN920 (mass-8-10 ⁶ ) at 0.01% stabilizes the emulsion and destabilizes it at higher concentration. In addition, at t = 0, there is an initial flocculation (by depletion) which explains the variation in initial size. It is observed that the addition of 0.5% of PNM flocculates the emulsion reversibly, at the start D ₅ o - 15 μm, and at t = 4 hours D ₅₀ - 3.5 m.

Figure 5 shows the stabilization under shear of an emulsion based on - 1% of PVA (φ = 40%, D ₅₀ ~ 1, 3 μm) containing polyacrylamide Floerger FN920 VHM (Mw> 8.10 ⁶ ) at l000ppm. Figure 5 shows the increased stabilization provided using a "very" high molecular weight PNM. There is almost perfect stabilization at 0.1%.

Table 3 presents the application properties observed for PNMs: all of these evaluations are good, especially the adhesion and reactivity, and in particular PNM with very high mass wets the support very well. The PNM with the highest mass is therefore the most effective, as is the POE.

Table 3: Application properties of emulsions stabilized with polyacrylamides

0.1% PNM (FN920) 0.1% PAM (FA920VHM)

Hrs hooked reactivity bπllanc wet cobb hooked reactivity bπllanc wet cobb

0 V V V

2 V V V

4 V V medium V

EXAMPLE 4

Guars constitute the third type of polymer evaluated. These are β 1,4 polysaccharides composed of a mannose skeleton with pendant galactoses. The galactose / mannose ratio is 2/1. The guar HP 105 is ur; hydroxypropylated guar of mass -600K with a degree of substitution of - 0.6.

An E 1.1 emulsion stabilized with 0.1% hydroxypropyl guar HP105 is used.

The reference used is E 1.1 without guar.

The average diameter of the HP 105 guar stabilized emulsion increases under shear: See Figure 6 which represents the average change in average size of an E l.l emulsion stabilized with 0.1% hydroxy propyl HP 105 guar.

Table 4 above gives the application properties of the emulsion with guar additive described above.

Table 4: Application properties of emulsions stabilized with hydroxy propyl guar HP105

0.1% HP GUAR 105 hrs hooked reactivity bπllanc cobb wet

0 V

2 V

4 V V V

Guar HP 105 stabilizes the emulsion satisfactorily, as does POE 2.

EXAMPLE 5

This example compares the performance of a silicone emulsion formulation containing polyethylene oxide compared to a formulation containing hydroxyethyl cellulose as a thickening agent.

The formulations are made from the same silicone emulsions:

• Silcolease 902 (RHODIN): emulsion of a mixture of vinylated and hydrogenated PDMS oil containing approximately 40% dry silicone extract. • Silcolease 903 (RHODIN): Pt catalyzing emulsion (PDMS oil more complex vinylized Pt) with about 40% dry silicone extract. These emulsions will be formulated in post addition (but this could be done at the time of the emulsion of the silicone oils) according to the cases with:

• HECules HEC 25 OH, as a thickener

• POE WSR 308 from Union Carbide (molar mass 8 x 10 ⁶ g / mole) and POE WSR coagulant from Union Carbide (mass 5 x 10 ⁶ g / mole).

The foam and the Dusts (deposits on the drying rolls of the coating line) are evaluated visually during the test and at the end of the test.

The composition of the 3 formulations used are given in Table 5 below.

Table 5: Formulations used

The results obtained with these different formulations are summarized in Table 6 below:

Table 6

They highlight:

• the stability to coalescence under shear brought by the POE, and all the more important as the mass of the polymer is high (stability test T described above); • the regularity and homogeneity of the silicon deposits measured in g / m ² by the X fluorescence method on an Oxford X-ray 3000 device) on both sides of the paper: these deposits were obtained after coating on size press and crosslinking at 130 ° C on a non-porous parchment paper backing; • the reduction of dusts (deposits of Silicones) evaluated visually on the rollers of the machine after coating;

• the removal of foam.

Claims

1 - Use of at least one hydrophilic stabilizing (co) polymer of mmoassssee mmoollar Mw> 1.10 g / mole, preferably Mw> 5.10 ⁵ g / mole

> to improve the stability to coalescence under shear of aqueous silicone emulsions capable of crosslinking to form non-stick coatings on flexible supports,

> and / or to improve the regularity and homogeneity of the deposit of crosslinkable aqueous silicone emulsions, on the two faces of flexible supports,

> and / or to reduce residual deposits on the cylinders of the coating machine, of silicone derived from aqueous silicone emulsions capable of crosslinking to form non-stick coatings on flexible supports,> and / or to limit or even eliminate the tendency to foam which the aqueous silicone emulsions capable of crosslinking have in order to form non-stick coatings on flexible supports.

2 - Use according to claim 1 characterized in that the stabilizer is chosen from the group of hydrophilic (co) polymers comprising:

* natural from animal origin such as chitosan and chitin in particular, * natural from vegetable origin: ^ such as in particular carrageenans, alginates, gum arabic, guar, carob, tara, cassia, konjak mannan; guars alginates, carob gums being more particularly appreciated, and / or starch and its derivatives and / or cellulose and its derivatives, carboxymethylcellulose, methylcellulose, ethylcellulose, hydroxymethylcellulose, cyanoethylated starch, the carboxymethyl starch being particularly selected; * and / or those of bacterial origin (biogums), in particular those obtained by fermentation of a carbohydrate under the action of a microorganism, xanthan gums obtained by fermentation under microorganisms belonging to the genus Xanthomonas;

-d- polyacrylates:

coord

Rd representing a linear or branched C1-C12 alkyl or a C5-C6 cycloalkyl.

3 - Use according to claim 2 characterized in that at least one stabilizer a or b is used, the Mw of which is such that:

Mw 1.10 ⁶ g / mole preferably Mw 3.10 ⁶ g / mole and in practice 20.10 ⁶ >Mw> 4.10 ⁶ . g / mol

and in that the concentration Cs, expressed in% by weight relative to the mass of POS of the emulsion, is such that:

0, 1 ≤ Cs <5 preferably 0, 5 <Cs <2. 4 - Use according to any one of claims 1 to 3 characterized in that a stabilizer - c - is used, the Mw of which (in g / mole) is such that:

more preferably still Mw> 1.10 ⁵ more especially still Mw> 3.10 ⁵ and in practice 20.10 ⁶ >Mw> 5.10 ⁵ .

and in that the concentration Cs of stabilizer in the emulsion, expressed in% by weight relative to the mass of the POS of the emulsion, is such that:

0.05 <Cs <5 preferably 0.1 <Cs <2

5 - Use according to any one of claims 1 to 4, characterized in that the stabilizer is selected so that the emulsion has the following particle size characteristics, as regards the dispersed silicone phase:

D _{50 7} μm, preferably 3 μm D ₉₀ 20 μm preferably 10 μm after 4 hours in a stability test T and for an initial particle size such as:

D ₅₀ 0.7 μm D ₉₀ 1.5 μm

6 - Use according to any one of claims 1 to 5, characterized in that the emulsion comprises at least one polyvinyl alcohol (PVA), preferably a PVA, whose dynamic viscosity ηdt is between 5 and 40 mPa.s and the degree of hydrolysis of which is between 80 and 98, preferably between 85 and 95.

7 - Aqueous silicone emulsion characterized in that it comprises:

- A - at least one polyorganosiloxane (POS) carrying Si-alkenyl crosslinking units, preferably Si-Vi; - B - at least one POS carrying Si-H crosslinking patterns;

- AB - and / or at least one POS carrying Si-alkenyl and Si-H units; - C - at least one polyaddition catalyst, preferably based on platinum;

- D - at least one stabilizer as defined in claims 2 to 5;

- E - at least one crosslinking inhibitor chosen from acetylenic alcohols;

- F - and / or at least one agent for fixing and maintaining the pH (preferably a buffer and more preferably still NaHCO ₃ );

- G - optionally at least one surfactant;

- H - optionally at least one polyvinyl alcohol APV as defined in claim 6;

- 1 - optionally at least one other additive chosen from bactericides, and / or anti-freeze agents, and / or wetting agents, and / or anti-foam agents and / or fillers, and / or synthetic latexes, and / or dyes, and / or acidifiers.

8 - Process for preparing the emulsion according to claim 7 characterized in that one carries out the emulsion of the silicone phase in the aqueous phase and in that one incorporates the stabilizer (co) hydrophilic polymer in the formulation before, during or after the formation of the aqueous silicone emulsion.

9 - Support characterized in that it comprises at least one non-stick coating obtained: ^" from an aqueous silicone emulsion for which the use according to any one of claims 1 to 6 is implemented, • and or from an emulsion according to claim 7 or 8.